Geo/Eco/Edu Info

Geo/Eco/Edu Info

Fleming Forestry Students on a Field Trip to the Lochlin Esker & Wetlands, Fall 2016

LOCHLIN ESKER & WETLANDS (Personal Perspectives)… D. Wright

During the most recent ice-age (estimated by earth scientists at between 10 and 12 thousand years ago), remarkable gouging and scouring of the land accounts for the rounded hills (peneplain feature) and elongated lake features. The second phase, the deglaciation, or melt and retreat of the glacier created a secondary set of interesting features such as moraine, drumlin, esker, and the remarkable bore holes in our area known as the “Harburn Wells”

Although the Lochlin Esker is not particularly large by comparison with other eskers in the province, its significance derives more as factors of its relative rarity in this area combined with placement in one of the larger wetland areas in Haliburton County.

Moving on an axis roughly parallel to the original glaciation (North-East to South-West), the Lochlin Esker meanders in some places from this course and thins it volume of sand and gravel. The serpentine meander is best explained by the realization of the fact that the “esker” is the accumulated debris (sand and gravel) of a once glacial river either internal (englacial) or underneath the glacier (subglacial). So, as it is the character of a river to experience bends or twists similarly, the esker feature formed during deglaciation presents itself in a “river” shape.

The Lochlin Esker strides boldly through the middle of one of the largest (within the top 8 percent) wetlands in the County! Directly the result of this placement, is the regulation, direction and movement of the waters being filtered and withheld for slow release in the five hundred acre wetland basin.

The Lochlin Esker is remarkably easy to become enthused about! It provides an easily maintained and travelled trail with spectacular views of the adjacent marsh, fen, bog, open areas. The esker is an intriguing mystery to those who care to consider, for example: (1) why is one face longer and steeper than the other ? (2) How does it happen that after so many years, it retains its shape? (3) What events caused directional and volume changes?

With the passage of time, this writer has come to consider the marriage of the Lochlin Esker to its surrounding wetlands as even more special. In a neat figure/ground reversal, it requires little imagination to realize that the undamaged wetlands, complete with rare orchid, beaver, black bear, sphagnum moss, pitcher plant, spruce bog, etc. are really very unique and clearly interrelated! In reality, neither esker nor wetland is complete without the undamaged counterpart.

To conclude, it seems to me the Designer well understood the need for integrity and connectedness amongst the several features of the Lochlin Esker. Remarkable for being a relatively “wild” area which is close to habitation, it seems to this writer that there are some things we really ought to leave alone. You are invited to visit and judge for yourself.

LOCHLIN ESKER/WETLANDS : GLOSSARY

The following terms and descriptions MAY prove helpful as supplementary to your memory when their usage occurs in the course of the flow of observations:

ANSI: (Area of Natural and Scientific Interest) Lochlin Esker and its outwash may in future be identified by the ANSI designation.(Confirmed as ANSI in 2015)

PSW: (Provincially Significant Wetland). In the summer of 2006, three biologists from the NHIC (Natural Heritage Information Centre, Peterborough) identified in the space of five hours some 242 species of flora. Of which, several were “rare” or “endangered” species. A “points” system evaluation then establishes if criteria warrant the PSW status. (Confirmed as PSW in 2014)

Esker: a long narrow, sinuous steep-sided ridge composed of irregularly stratified sand and gravel that was deposited by a subglacial or englacial stream flowing between ice walls or in an ice tunnel of a stagnant or retreating glacier, and was left behind when the ice melted. It may be branching and is often discontinuous, and its course is usually at a high angle to the edge of the glacier. Eskers range in length from less than 100 m to more than 500 km (if gaps are included), and in height from 3 to more than 200 m. (Source: Glossary of Geology, 4th ed.)

Esker (formation): Formation owing to a “retreating edge of an ice sheet, or an ice-walled tunnel. Subglacially engorged eskers are deposited in subglacial or englacial ice tunnels; to be preserved these tunnels must have been in stagnant ice.” (Source: A Dictionary of Ecology by Michael Allaby)

G.L.O.F.: “A Glacial Lake Outburst Flood (GLOF) can occur when a lake contained by a glacier (called Jokulhlaup if it was a subglacial lake, marginal lake drainage if it was dammed between ice and the ground) or a terminal moraine dam fails. This can happen due to erosion, a buildup of water pressure, an avalanche of rock or heavy snow, an earthquake or cryoseism, volcanic eruptions under the ice, or if a large enough portion of a glacier breaks off and massively displaces the waters in a glacial lake at its base.” (Source: Wikipedia)

Jokulhlaup: “is thus a sub-glacial outburst flood. Jokulhlaup is an Icelandic term that has been adapted into the English language, and originally only referred to glacial outburst floods from Vatnajokull, which are triggered by volcanic eruptions, but now is accepted to describe any abrupt and large release of sub-glacial water. (Ibid.)

Wetland: a general term for a group of wet habitats, in common use by specialists in wildlife management. It includes areas that are permanently wet and/or intermittently water-covered. (Source: Glossary of Geology, 4th ed.) At least four clearly observable wetland subgroups at Lochlin: (1) Open marsh (beaver pond) (2) Fen (3) Black Spruce Bog (4) Mixed treed bog

Fen: deposits consisting of sedge peat derived primarily from sedges with inclusions of partially decayed stems of shrubs formed in a eutrophic environment due to the close association of the material with mineral-rich waters. (Source: Canadian System of Soil Classification, 3rd edition.)

Peat: an unconsolidated deposit of semi-carbonized plant remains in a water-saturated environment such as a bog or fen, and of persistently high moisture content (at least 75%). When dried, peat burns freely. (Source: Glossary of Geology, 4th ed.)

Till: (aka Drift or Diamict) a sediment that has been transported and deposited by or from glacier ice with little or no sorting by water. (Source: Dreimanis 1982) Till is often poorly sorted, commonly containing clasts of many sizes in a variable finer-grained matrix. Till is composed of a mixture of minerals and rock types, some of which may be far-travelled. (Source Barnett 1992)

Moraine: a) a wide variety of depositional features collectively defining a linear landform produced by the complex interactions of numerous glaciogenic and paraglacial processes at the present and former margins of glaciers and ice sheets. The outermost moraine formed at the limit of a glacier advance is known as a terminal moraine. (Source Modified from,: Benn and Evans (1998) b)ridge of unconsolidated sediment, which defines an ice front position. Generally metres or tens of metres in height and hundreds of metres to several kilometers in length, occasionally hundreds of kilometers. (Source: GSC Working Group on the Canadian Glacial Landforms and Flow Indicators Database.)

Moraine: (a) (material) A mound, ridge, or other topographically distinct accumulation of unsorted, unstratified glacial drift, predominantly till, deposited primarily by the direct action of glacier ice, in a variety of landforms. (b) (landform) A general term for a landform composed mainly of till that has been deposited by a glacier; a kame moraine is a type of moraine similar in exterior form to other types of moraines but composed mainly of stratified outwash materials. Types of moraines include: end, ground, kame, lateral, recessional, and terminal moraines. Source: National Soil Survey

Crest: the highest point or line of a landform, from which the surface slopes downward in opposite directions; esp. the highest point of a mountain or hill or the highest line or culminating ridge of a range of mountains or hills. (Source: Glossary of Geology, 4th ed.)

Stagnant Ice/Esker Rarity Haliburton Region: “The overall pattern of glacial sedimentation within the Haliburton region suggests that most deposition occurred during ice retreat, within the proglacial and ice-marginal environments. The prevalence of ice contact terraces as the dominant glacial landform indicates that stagnation was an important element in the style of deglaciation. Although evidence for stagnation is observed in all depositional environments, evidence for regional ‘in situ’ down wasting of large masses of ice, such as the well integrated esker networks marking the disintegration of the central portion of the Laurentide Ice Sheet (Shilts et al., 1987), is not present.” (Conclusions, P. 181 Kaszycki paper 1996)

Tunnel valley/channel: a) large, over-deepened channel cut into bedrock or sediment, which can attain lengths of greater than 100 km and widths in excess of 4 km. They can occur in isolation or as parts of dendritic or anastamosing patterns extending over very large areas. They share many characteristics with Nye channels, including undulatory bed-long profiles, overdeepened basins along their floors and hanging tributary valleys. Individual tunnel valleys usually have wide, relatively flat bottoms and steep sides, and the numerous troughs that occur along their lengths may be occupied by lakes. They are excavated by subglacial meltwater flowing under hydrostatic pressure. They also tend to terminate at major moraines where they may grade into large subaerial ice-contact fans. (Source: Benn and Evans (1998) b) channel interpreted to have formed underneath a glacier, commonly with an undulating thalweg. (Source: GSC Working Group on the Canadian Glacial Landforms and Flow Indicators Database.)